The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An electronic thermostat is a technology to control a flow rate by adjusting a switching valve according to a state of an engine, and a partial control of a coolant flow rate is desired for enhancement of fuel consumption.
Particularly, fuel consumption may be modified through a technique separately cooling a cylinder head and a cylinder block, however two or more thermostats are generally desired for this.
That is, a head thermostat of a main thermostat controlling an engine exit coolant temperature and a block thermostat which controls the coolant temperature of the block to separately cool the cylinder head and the cylinder block must be provided.